The chromium spin density wave: magnetic X-ray scattering studies with polarisation analysis

We report on X-ray magnetic diffraction studies of the spin density wave an tiferromagnetism formed in the conduction electron band of chromium. Non-re sonant X-ray magnetic scattering was used to directly determine that chromi um has zero orbital magnetisation. Furthermore, the azimuthal dependence of this scattering provides unique evidence that chromium forms a linearly po larised wave. In the vicinity of the K absorption edge, resonant X-ray magn etic scattering was observed. A consistent model of the magnetic scattering has been derived from the resonant and non-resonant magnetic amplitudes. T he enhancement of the magnetic intensity arises primarily from dipole trans itions from the core Is level to 4p states. Quadrupole transitions to the m agnetic 3d states are essentially non-existent due to their sensitivity to land the absence of) orbital moment. This effect is predicted from atomic c onsiderations of the 3d(5) (L = 0) transition metal ions.